But wait a minute: stress doesn't cause colds, viruses cause colds, right? That's right. But when you are stressed out, you overproduce cortisol, making the immune system incapable of turning "off" the inflammation switch. The bottom line is that if you're exposed to a cold virus while you are also dealing with chronic stress — say at work or in your marriage — you are much more likely to get the cold and suffer from more intense symptoms than if you were not stressed out.

"The symptoms of a cold are not caused directly by the virus, they're caused by the inflammatory response to the infection," said Sheldon Cohen, a professor of psychology at Carnegie Mellon University in Pittsburgh and lead author of the study. "You want to produce enough of inflammation to fight off the infection, but not so much that you experience cold symptoms."

The findings also suggest that other illnesses, such as asthma, cardiovascular disease, and autoimmune disorders may be similarly affected by stress.

Do yourself and your runny nose a favor and find a way to ease your stress — at least until the next cold comes along!